Photothermographic element and process

ABSTRACT

Hydroxamic acid reducing agents in a photothermographic element or process for developing a latent image with heat provide a developed image having increased maximum density. They can be employed in an oxidation-reduction image forming combination wherein the hydroxamic acid is used as the reducing agent. Addenda employed in photothermographic elements and processes, such as activator-toning agents, sensitizing dyes and stabilizer precursors can be employed with the hydroxamic acid reducing agents.

United States Patent [1 1 Smith et a1.

P11 ()TOTH ERMOG RAPHIC ELEM ENT AND PROCESS Inventors: Gale E. Smith; Paul Hartman, both of Rochester, NY.

Eastman Kodak Company, Rochester, N.Y.

Filed: Mar. 24, 1972 Appl. No.: 237,932

Assignee:

US. Cl 96/63, 96/48 HD, 96/67, 96/114.1, 96/1146, 117/36.8, 117/369, 250/65 T Int. Cl G031: 1/60, G036 1/72 Field of Search 96/67, 114.1;

References Cited UNITED STATES PATENTS 5/1928 Schestakoff 96/665 [111 3,751,252 1 Aug. 7, 1973 3,429,706 2/1969 Shepard 96/1 14.1 3,645,739 2/1972 ()hkubo 961114.] 3,667,958 6/1972 Evans 96/1 14.1

Primary ExaminerNorman G. Torchin Assistant ExaminerA1f0ns0 T. Suropico AttorneyRobert W. Hampton et a1.

[ 57] ABSTRACT sensitizing aye; aha stabilizer preciirsors'can be employed with the hydroxamic acid reducing agents.

17 Claims, No Drawings BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to photosensitive elements, compositions and processes for developing a latent image using certain reducing agents in so-called dry processing with heat. In one of its aspects it relates to a photothermographic element employing an oxidation-reduction image fonning combination of l) a heavy metal salt oxidizing agent with (2) certain hydroxamic acid reducing agents. This oxidationreduction image forming combination can be employed with photosensitive silver halide. A further aspect relates to a process of developing a latent image in a photothermographic element by heating the element which contains the described oxidation-reduction image forming combination.

2. Description of the State of the Art It is known to develop a latent image in a photographic silver halide element using a silver halide developing agent in so-called dry processing with heat. The photographic element can contain a silver halide developing agent as well as a stabilizer component. After exposure, the resulting image can be developed and stabilized by heating the photographic element. Such a process is described, for example, in U.S. Pat. No. 3,301,678 of Humphlett et al. issued Jan. 31, 1967.

Other methods of so-called dry processing with heat are described, for example, in U.S. Pat. No. 3,152,904 of Sorensen et al. issued Oct. 13, 1964; U.S. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969; British Pat. No. l,l6l,777 published Aug. 20, 1969; Belgian Pat. No. 705,872; U.S. Pat. No. 2,910,377 of Owen issued Oct. 27, 1959; and U.S. Pat. No. 3,392,020 of Yutzy et al. issued July 9, 1968.

While many reducing agents have been employed in elements and compositions containing an oxidationreduction image forming combination of an oxidizing agent and a reducing agent, especially in the presence of catalyst, such as photosensitive silver halide, some of these have not provided the desired increased maximum density or desired tone in the developed image satisfactorily. For example, a hydroquinone reducing agent which has been employed in such a combination has not provided a sufficiently dense-black image and moreoever, the background of the developed image is not desirably clean, that is, undesired print out in th background areas of the print occurs.

A hydroxamic acid derivative of the formula has been disclosed along with a primary amino aromatic developing agent for the production of color images in deCat et al U.S. Pat. No. 2,668,] 12 issued Feb. 2, I954. Schestakoff U.S. Pat. No. 1,663,959 issued Mar. 27, 1928 discloses a hydroxamic acid having the formula "i C-NHOH in a silver halide developer solution containing hydroquinone to reduce contrast, fogging, etc. However, hydroxamic acids have shown littledeveloping activity for silver halides so their use in heat processing is unexpected.

Accordingly, it is an object of the invention to provide certain hydroxamic acid reducing agents in a photo-thermographic element or process employing an oxidation-reduction image forming combination as described.

SUMMARY OF THE INVENTION It has been found, according to the invention, that in a photothermographic element and process employing such an element that a hydroxamic acid reducing agent can be used in an oxidation-reduction image forming combination with a catalyst for the image forming combination such as a radiation-sensitive silver salt.

DETAILED DESCRIPTION OF THE INVENTION A range of hydroxamic acids can be employed according to the invention. Any hydroxamic acid can be employed which in the described image forming com bination after exposure and upon processing with heat provides desired density without undesired backgroun print-out. V

Hydroxamic acids which are suitable include compounds of the formula:

where R is alkyl containing one to 12 carbon atoms, such as methyl, ethyl, propyl, butyl and pentyl, aryl containing six to 12 carbon atoms, such as phenyl, and naphthyl, a 5 to 7 member nitrogen containing heterocyclic ring such as morpholino, pyridino, piperidino, pyrrolidino, piperazino, hexamethyleneimino and methylpiperidino. R can contain various substituents, e.g., hydroxy, amino, halogen, carboxy, sulfonyl and the like.

Examples of compounds included in the above structure are:

B-Pyridylhydroxamic acid.

(b) ei-F uryl hydroxamic acid.

i la -N011 \0 n 1 (c) (lf1;IOH Phenyl hydroxamic aid.

((1) V 7 p-Hydroxy phenyl hydroxamic -%III H acid.

0 H O H- (c) II II Oxalohydroxamic acid.

Photothermographic elements which are suitable for processing with heat according to the invention are believed to provide a developed image by physical development. Photothermographic elements in which one or more of the described hydroxamic acid reducing agents can be employed are described, for example, in US. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969; U.S. Pat. No. 3,429,706 of Shepard et al. issued Feb.- 25, 1969; US. Pat. No. 3,152,904 of Sorensen et al. issued Oct. 13, 1964; U.S. Pat. No. 3,392,020 of Yutzy et al. issued July 9, 1968; US. Pat. No. 3,152,903 of Shepard et al. issued Oct. 13, 1964 and Belgian Pat. No. 705,872. In photosensitive elements, as described, typically a support is provided with an oxidation-reduction image forming combination comprising an oxidizing agent, typically a silver salt oxidizing agent which is a silver salt of a fatty acid, with an organic reducing agent, and a catalyst for the image forming combination, such as photosensitive silver halide. A visible image is produced after exposure of the photosensitive element within a few seconds after exposure by heating the element to moderately elevated temperatures, e.g. about 80C to about 250C.

Accordingly, one embodiment of the invention is a photothermographic element comprising a support, photosensitive silver halide, and an oxidation-reduction image forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a hydroxamic acid reducing agent.

The described hydroxamic acids can be prepared by methods known in the chemical art.

A photothermographic element according to the invention can comprise a support, photosensitive silver halide, and an oxidation-reduction image forming combination comprising a heavy metal salt oxidizing agent with a hydroxamic acid, as described.

The described hydroxamic acid reducing agents can be employed in a photothermographic element or composition containing a complex of silver as the photosensitive salt, such as a silver-dye complex. Such a photothermographic element can comprise a support, a silver-dye salt, a hydroxamic acid reducing agent, a source of a metal for physical development, especially a source of silver for physical development, such as silver behenate or silver stearate, and a binder, typically polyvinyl butyral. Suitable silver-dye complexes or salts are described in US. Pat. No. 3,446,619 of Gilman et al. issued May 27, 1969.

The described element or composition contains a catalyst for the image-forming combination, especially a photosensitive silver salt. A typical concentration range of photosensitive silver salt is from about 0.005 to about 0.50 mole of silver salt per mole of oxidizing agent such as per mole ofsilver salt of organic acid, e.g., per mole of silver behenate. A preferred catalyst is photosensitive silver halide, e.g., silver chloride, silver bromide, silver chloroiodide, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. The photosensitive silver halide can be coarse or fine-grain, very fine-grain silver halide being especially useful. The emulsion containing the photosensitive silver halide can be prepared by any of the well-known procedures in the photographic art, such as single-jet emulsions, double-jet emulsions, such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions, such as those described in US. Pat. No. 2,222,264 of Nietz et al. issued Nov. 14, 1940;U.S. Pat. No. 3,320,069 of lllingsworth issued May 15, 1967 and US. Pat. No. 3,271,157 of McBride issued Sept. 6, 1966. Surface image silver ha lide can be used. If desired, mixtures of surface and internal image silver halide emulsions can be used as de' scribed in US. Pat. No. 2,996,332 of Luckey et al. issued Apr. 15, 1961. Negative type emulsions can be used. The silver halide can be a regular grain silver ha lide such as described in Klein and Moisar, Journal of Photographic Science, Volume 12, No. 5, September- October (1964) pages 242-251.

Suitable silver halide emulsions, preparations, addenda, processing and systems are disclosed in Product Licensing Index, Vol.92, December, 1971, publication 9232, pages 107-1 10, paragraphs Il-V and Vll-X Vlll.

Other suitable organic reducing agents which can be employed in combination with the described hydroxamic acids include, for example, substituted phenols and naphthols. For example, a bis-B-naphthol of the formula:

wherein R, and/or R is hydrogen, alkyl with one to three carbon atoms, alkoxy, e.g., alkoxy containing one to two carbon atoms, such as methoxy or ethoxy; halogen, nitro, amino or a diazonium halide salt and n is 0 or 1 can be employed. Suitable bis-B-naphthols which can be employed include:

.2'5Qlill9593l'fl132 39932!!! 6,6 -Dibromo-2,2 '-dihydroxy-l ,1 -binaphthy1,

6,6'-Dinitro-2,2'-dihydroxy-1,l '-binaphthyl, and/or Bis-(2-hydroxy-1-naphthyl)methane.

The described elements and compositions comprise a heavy metal salt oxidizing agent, typically a heavy metal salt of an organic acid. The heavy metal salts of the organic acids should be resistant to darkening under illumination to prevent undesired deterioration of a developed image. An especially suitable class of heavy metal salts of organic acids is represented by thewater insoluble silver salts of long-chain fatty acids which are stable to light. Compounds which are suitable silver salts include silver behenate, silver stearate, silver oleate, silver laurate, silver hydroxystearate, silver caprate, silver myristate and silver palmitste.

Other suitable carboxylic acid silver salt oxidizing agents, which are not silver salts of long-chain fatty acids include silver benzoate, silver 4'-noctadecyloxydiphenyl-4-carboxylate, silver 0- aminobenzoate, silver acetamidobenzoate, silver furoate, silver camphorate, silver p-phenylbenzoate, silver phenylacetate, silver salicylate, silver butyrate, silver terephthalate, silver phthalate, silver acetate and silver acid phthalate.

Oxidizing agents which are not silver salts of a carboxylic acid can be employed, if desired, such as silver phthalazinone, silver benzotriazole and silver saccharin. Oxidizing agents which are not silversalts can be employed, if desired, such as zinc oxide, gold stearate, mercuricbehenate, auric behenate and the like, but silver salts are preferred.

It is often desirable to employ a so-called activatortoning agent in the elements, compositions and ,processes of the invention to obtain a desired image. However, in some cases this is not necessary when employing the reducingagents of the invention. This is demonstrated in the following examples.

The described activator-toningagents are suitable in a wide range of concentrations; however, they are especially suitable at concentrations of about 0.10 mole to about 1.05 moles of activator-toning agent per mole of oxidizing agent, e.g., per mole of silver behenate.

A suitable activator-toning agent is a heterocyclic activator-toning agent .containing at least one nitrogen atom and having the formula:

wherein R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z representsatoms completing a heterocyclic nucleus, especially 5 or 6 member heterocyclic nucleus. The atoms completing the hetero-cyclic nucleus can be, for example,

or an alkylene group containing three to four carbon atoms. The atoms completing the heterocyclic nucleus can contain various substituent groups, such as amino, alkyl amino, e.g., methylamino or ethylamino, hydroxyl, carbamyl and the like. An especially suitable activator-toning agent is a heterocyclic activatortoning agent containing at least one nitrogen atom which is preferably a cyclic imide of the formula:

wherein R can be hydrogen, hydroxyl, or a metal ion such as potassium, sodium lithium, silver, gold or mercury; Z, represents carbon atoms of a series completing a cyclic imide nucleus, typically consistingof from five to six carbon atoms, e.g., a phthalimide or succinimide nucleus. The atoms of the cyclic imide nucleus can contain various substituent groups, especially amino, alkyl, such as alkyl containing one to five carbon atoms, such as methyl,-ethyl,.,propyl,butyl, or pentyl or aryl, such as aryl containing six to 20 carbonatoms, such as phenyl, tolyl and xylyl. Suitable activatortoning agents which can be employed'in the practice of the invention include:

Phthalimide,

, N-Hydroxyphthalimide,

N-Potassium phthalimide,

N-Silver phthalimide,

N-Mercury phthalimide,

Succinimide, and/or N-H'ydrox-ysuccinimide.

Other so-called activator-toning agents can be employed incombination'withorin'place of the described cyclic imide activator-toning agents. Typically a heterocyclic organic toning agent containing at least two hetero atoms in the heterocyclic ring of which at least one is a nitrogen atom is employed. These are described, for example, in US. Pat. No. 3,080,254 of Grant issued Mar. 5, i963. Suitable tonersinclude, for example, phthalazinone, Z-acetylphthalazinone and 2- phthalylphthalazinone. Other suitable toners are described, for example, in US. Pat. No. 3,446,648 of Workman issued May 27, 1969. t

A divalent metal salt which has the property of amplifying the developed image can be employed in the practice of the invention to cause an increase in maximum image density. A suitable divalent metal salt image amplifier is zinc acetate, cadmium acetate or cupric acetate. The described image-amplifying compounds are suitable in a range of concentration of about 0.005 to about 0.20 mole of divalent metal salt image amplifier per mole of heavy metal salt oxidizing agent; however, they are especially suitable at a concentration from about 0.010 mole to about 0.10 mole of divalent metal salt image amplifier per moleof heavy metal salt oxidizing agent.

It is desirable in some cases to employ an image stabilizer percursor in the described elements of the invention. These can be employed in the practice of the invention to reduce the amount of post-processing printout due to room light exposure and to reduce the background stain. Suitable stabilizer precursors include, for example, azole thioethers and blocked azole thione stabilizer precursors, e.g., 5-acetyl-4-methyl-2-(3- oxobutylthio )thiazole, 4-furoyl-3-methylthio-l ,2,4- thiadiazole-S-thione, 5-acetyl-4-methyl-3-( 3- oxobutyl)-thiazoline-2-thione and 2,6-di-tert-butyl-4- (l-phenyl-5-tetrazolyl)thiophenol. The described stabilizer precursors are suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.002 mole to about 0.10 mole of stabilizer precursor per mole of oxidizing agent, e.g., per mole of silver behenate, in an element as described.

A range of colorless onium halides can be employed in the described elements to provide an additional increase in photosensitivity, i.e., speed, an d in some cases to obtain a reduction in background density. A suitable speed-increasing onium halide compoundis a quaternary ammonium halide, quaternary phosphonium halide and/or a tertiary sulfonium halide, e.g., l-phenethyl-2-picolinium bromide, tetraethylphosphonium bromide or trimethylsulfonium iodide. An optimum concentration can be determined for each onium halide. An especially suitable onium halide is a trimethylphenylammonium bromide which is typically employed at a concentration of about 0.010 mole to about 0.05

mole per mole of catalyst, e.g., per mole of photosensitive silver halide.

A photothermographic element described and used in the practice of the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers.

Preferred materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, poly(vinyl pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloridevinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and polyvinyl alcohol.

If desired, the photosensitive silver halide can be prepared in situ, in the photothermographic coatings of an element employed in the practice of the invention. Such a method is described, for example, in U.S. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969. For example, a dilute solution of a halogen acid such .as hydrochloric acid, can be applied to the surface of a thin coating containing an organic silver salt, such as silver behenate, on a suitable subtrate followed by removal of the solvent if desired. Silver halide is thus formed in situ throughout the surface of the coating of the organic silver salt.

The photosensitive silver halide can be prepared on the oxidizing agent, such as silver behenate or silver stearate, or other organic silver salt, prior to application of the silver halide on the support employed. This is also described in U.S. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969, for example, a halogen acid such as hydrochloric acid or hydrobromic acid can be mixed with an organic silver salt in a suitable reaction medium. A halide salt more soluble than the organic,

silver salt can be added to a suspension of the organic silver salt to form the silver halide. A suitable reaction medium includes water or other solutions which do not interfere with the reaction.

Stability to print out from light exposure is increased by employing highly purified materials; for example, freedom from halides and sulfides increase stability to light exposure. The use of highly purified silver behenate can, for example, reduce propensity to print out in background areas of an element prepared according to the invention.

A range of concentration of spectral sensitizing dye can be employed in the practice of the invention to provide spectral sensitivity. The desired concentration will be influenced by the desired spectral sensitivity, other components in the system, the desired image, processing conditions and the like. Typically a concentration of the described spectral sensitizing dye is typically about 50 mg. to about 2 grams of spectral sensitizing dye per mole of catalyst, e.g., per mole of photosensitive silver halide.

While the concentration of the various components of the described element or composition can vary depending upon the desired image, the particular components, processing temperature and time and the like, the described element or composition can typically contain about 0.05 to about 3.0 moles of the described reducing agent per mole of described oxidizing agent, and about 0.005 to about 0.50 mole of the described catalyst per mole of described oxidizing agent.

For example, a typical photothermographic composition or element can comprise photosensitive silver halide, an oxidizing agent, which comprises silver behenate,

a. about 0.05 to about 4.0 mole of hydroxamic acid reducing agent per mole of silver, preferably about 0.2 to about 1 mole/mole silver,

b. about 0.005 to about 0.50 mole of photosensitive silver halide per mole of silver behenate oxidizing agent and, usually c. about 0.10 mole to about 1.05 moles of phthalimide or phthalazinone activator-toning agent per mole of silver behenate.

An especially suitable photothermographic element or composition, as described, comprises:

a. polyvinylbutyral binder,

b. an oxidizing agent comprising silver behenate,

c. a reducing agent comprising a hydroxamic acid, as

described,

d. photosensitive silver halide,

e. phthalimide activator-toning agent,

f. zinc acetate image amplifier,

g. l-phenethyl-Z-picolinium bromide or trimethylphenylammonium bromide,

h. a stabilizer precursor, such as 5-acetyl-4-methyl-2- (3-oxobutylthio)thiazole, and

i. a blue speed-increasing sensitizing dye, such as 3- carboxymethyl-5-[(3-methylr2(3l-l)- thiazolinylidene)-isopropylidenelrhodanine, ethyl-5-[(3-ethyl-2(3H)- benzothiazolylidene)isopropylidene]-2-thio-2,4- oxazolidenedione or 1-carboxymethyl-5-[(3-ethyl- 2(3H)-benzoxazolylidene)-ethylidene]-3-phenyl- 2-thiohydantoin.

After exposure of the described photothermographic element, the resulting latent image is developed merely by heating the element. Accordingly, another embodiment of the invention is: a process comprising heating the described element to about C to about 250C, such as, for about 0.5 second to about 60 seconds.

A temperature range of about C to about C is usually suitable for developing and stabilizing a desired image. By increasing or decreasing the length of time of heating, a higher or lower temperature within the described range can be employed. A developed image is typically produced within a few seconds such as about 0.5 second to about 60 seconds, usually in about 0.5 to about 10 seconds.

The photographic process can comprise, for example, exposing to actinic radiation a photothermographic element comprising a support,

a. photosensitive silver halide,

b. an oxidation-reducing image-forming combination comprising 1. silver behenate with 2. a hydroxamic acid reducing agent, as described, comprising heating said element to about 80C to about 250C for about 0.5- second to about 10 seconds.

When a stabilizer or stabilizer precursor is employed in the described element and/or composition improved stability against post-processing print out is provided. Accordingly, another embodiment of the invention is a process of developing and stabilizing an image in an exposed photosensitive element comprising a support,

a. photosensitive silver halide,

b. an oxidation-reduction image-forming combination comprising i. a heavy metal salt oxidizing agent as described with ii. a hydroxamic acid reducing agent, as described,

and c. a stabilizer precursor comprising heating said element to about 80C to about 250C.

The time required for development and stabilization can vary depending on the particular stabilizer precursor, particular developing agent, processing temperature and the like. However, usually a developed and stabilized image results within several seconds, such as about 0.5 to about 60 seconds.

Processing is usually carried out under ambient conditions. Temperatures, pressures and humidity outside normal atmospheric conditions can be employed if desired; however, normal atmospheric conditions are preferred.

Any suitable means can be used for providing the desired processing temperature range. The heating means can be a simple hot plate, iron, roller or the like.

In some cases, if desired, an element can be prepared wherein one or more components, such as the described silver halide, can be in one layer and other components in other layers. For example, an element according to the invention can comprise a support, a layer containing photographic silver halide and a layer comprising the so-called oxidation-reduction imageforming combination comprising:

a. a heavy metal salt oxidizing agent, as described,

e.g., silver behenate with,

b. a hydroxamic acid reducing agent, as described.

A typical so-called oxidation-reduction imageforming composition comprises, according to the invention: I

a. silver behenate,

b. a hydroxamic acid reducing agent, as described,

and

c. phthalimide or phthalazinone.

Typically, a polyvinylbutyral binder is employed with this so-called image-forming composition.

Other addenda known to be useful in photothermographic elements, such as described in British Pat. No. 1,161,777 published Aug. 20, 1969; U.S. Pat. No. 3,15- 2,904 of Sorensen and Shepard issued Oct. l3, I964 and U.S. 'Pat. No. 3,457,075 of Morgan and Shely patented July 22, 1969 can be employed in the practice of the invention; i

The following examples are included for a further understanding of the invention.

EXAMPLE 1 Developing Activity A mixture of silver behenate and behenic acid as described in US. Pat. No. 3,457,075 of Morgan et al. issued .luly 22, 1969 is prepared by precipitation with silver nitrate from a solution of sodium behenate and behenic acid in non-polar solvent. The precipitate is thoroughly washed and dried.

A coating composition is prepared by mixing the following components:

by volume) After ball-milling for about 18 hours, 75.0 ml of an acetone solution containing 1 percent by weight of lithium bromide is added to the above dispersion and the mixture is stirred for about 18 hours during which time silver bromide is formed in situ. The resulting dispersion is coated on a paper support'at a wet thickness of 0.006 in. The resulting coating is dried. Four compounds as shown in Table I are dissolved at 0.02 molar concentration in anacetone-alcohol solution. The solutions are then spotted onto the coatings with a glass stirring rod and dried. in replicate tests the coatings are also-spotted with a 0.02 molar solution of phthalazinone toning agent aswell as the developingagent being tested. Again the coating is dried. The coatings are then exposed to light and heated on a mandril at 140C. All of the agents produce appreciable density, even in the absence of the toning agent. The aryl hydroxamic acids produce particularly high density, even in the absence of the toning agent. These data are given in Table I.

With the addition of phthalazinone toning agent. High density represents a density of about 0.8-1.0. Medium density represents a density of about 0.5-0.8.

' EXAMPLE 2 Usefulness with Incorporated Activator-Toner A coating similar to that of Example 1 is prepared ex-. cept that phthalazinone is incorporated in the coating as a toner. A 0.02 molar solution of either Compound I or II is coated over this emulsion and dried. This emulsion, now containing the hydroxamic acid, is exposed to a graphic test object and processed by contact with a heated mandril at C. Useful images of good density range are produced. Similar results are obtained with a coating employing phthalimide as an activatortoner to replace the phthalazinone.

EXAMPLE 3 Usefulness without Accelerator-Toner Coatings are prepared with 10 ml of melt which 2 ml of a dispersion and 0.04 mmols of a hydroxamic developing agent, selecting compounds I, II and The dispersion contains silver behenate, behenic acid,

polyvinylbutyral, sodium bromide and acetone/toluene solvent as described in Example I. A 5 mil layer of melt is coated on polyethylene coated paper, utilizing a coating knife and block.

After drying, a sample of the coating is exposed to a graphic test object and heated incontact with a platen at 115C. Results reported in the following Table ll show that good image discrimination can be obtained in the absence of toner. Such a result is unexpected and use unusual in prior art systems. Densities are measured using an Eastman II B Densitometer.

8. An element as in claim 1 further comprising an activator-toning agent.

TABLE II Compound I Compound II Compound IV Activator Dev.

toner agent Time Time Time (mmols) (mmols) (sec) Dmax. Dmin. (see) Dmax. Dmin. (sec.) Dmax. Dmin.

None 0.04 12 .32 .09 7 .24 .04 8 .44 .28 0.04 .02 25 .16 .06 13 .14 .01 12 .34 .29 .04 .04 14 .21 .07 8 .21 .05 7 .40 .12 .04 .08 12 .20 .08 8 .30 .06 8 .34 12 mg the formula: T

wherein R is alkyl containing one to 12 carbon atoms, aryl containing six to 12 carbon atoms, or a -7 member N containing heterocyclic ring.

2. A phototherrnographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:

3. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:

4. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:

HO-Qfi-NHOH 5. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:

6. A photosensitive and thermosensitive element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:

I 7. A photosensitive and thermosensitive element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:

II i

9. An element as in claim 1 further comprising phthalazinone or phthalirnide.

10. An element as in claim 1 further comprising a divalent salt image amplifier.

11. An element as in claim 1 further comprising zinc acetate.

12. An element as in claim 1 further comprising a stabilizer precursor.

13. A photothermographic element as in claim 1 comprising about 0.l 0 to about 4 moles of said reducing agent per mole of silver in said element and about 0.005 to about 0.50 mole of said photosensitive silver halide per mole of said oxidizing agent.

14. A photothermographic element as in claim 1 comprising,

a. photosensitive silver halide,

b. an oxidation-reduction image-forming combination comprising i. silver behenate with ii. a hydroxamic acid reducing agent,

c. a polyvinyl butyral binder and d. an activator-toning agent which is phthalazinone or phthalimide.

15. A process of developing a latent image in an exposed photothermographic element comprising a photosensitive silver halide, and an oxidation-reduction image-forming combination comprising (i) an oxidizing agent with (ii) a hydroxamic acid reducing agent having the formula:

wherein R is alkyl containing one to 12 carbon atoms, aryl containing six to 12 carbon atoms, or a 5-7 member N containing heterocyclic ring.

16. A process as in claim 15 comprising heating said element to about C to about 250C for about 0.5 second to about 10 seconds.

17. A process as in claim 15 of developing a latenttwp-onion wherein R is alkyl containing one to 12 carbon atoms, aryl containing six to 12 carbon atoms, or a 5-7 member N containing heterocyclic ring comprising heating said element to about 80C to about 250C for about i 0.5 to about 10 seconds. 

2. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:
 3. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:
 4. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has tHe formula:
 5. A photothermographic element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:
 6. A photosensitive and thermosensitive element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:
 7. A photosensitive and thermosensitive element as in claim 1 wherein said hydroxamic acid reducing agent has the formula:
 8. An element as in claim 1 further comprising an activator-toning agent.
 9. An element as in claim 1 further comprising phthalazinone or phthalimide.
 10. An element as in claim 1 further comprising a divalent salt image amplifier.
 11. An element as in claim 1 further comprising zinc acetate.
 12. An element as in claim 1 further comprising a stabilizer precursor.
 13. A photothermographic element as in claim 1 comprising about 0.10 to about 4 moles of said reducing agent per mole of silver in said element and about 0.005 to about 0.50 mole of said photosensitive silver halide per mole of said oxidizing agent.
 14. A photothermographic element as in claim 1 comprising, a. photosensitive silver halide, b. an oxidation-reduction image-forming combination comprising i. silver behenate with ii. a hydroxamic acid reducing agent, c. a polyvinyl butyral binder and d. an activator-toning agent which is phthalazinone or phthalimide.
 15. A process of developing a latent image in an exposed photothermographic element comprising a photosensitive silver halide, and an oxidation-reduction image-forming combination comprising (i) an oxidizing agent with (ii) a hydroxamic acid reducing agent having the formula:
 16. A process as in claim 15 comprising heating said element to about 80*C to about 250*C for about 0.5 second to about 10 seconds.
 17. A process as in claim 15 of developing a latent image in an exposed photothermographic element comprising a support, a. photosensitive silver halide, b. an oxidation-reduction image-forming combination comprising: i. silver behenate and ii. a hydroxamic acid reducing agent comprising a compound of the formula: 